1. Technical Field
Embodiments of the present invention are directed to lithium secondary batteries.
2. Description of Related Art
Batteries transform chemical energy (generated from an electrochemical redox reaction of a chemical material in the battery) into electrical energy. Such batteries are classified as primary batteries, which should be disposed of after all the energy of the battery is consumed, and rechargeable batteries, which can be recharged many times. Rechargeable batteries may be charged/discharged many times due to the reversible transformation of chemical energy to electrical energy.
Recent developments in high-tech electronics have allowed electronic devices to become small and light in weight, leading to an increase in portable electronic devices. As the power sources for such portable electronic devices, the demand for batteries having high energy density is increasing, and research is being conducted into lithium rechargeable batteries.
The lithium secondary battery is fabricated by injecting an electrolyte into an electrode assembly. The electrode assembly includes a positive electrode including a positive active material capable of intercalating/deintercalating lithium, and a negative electrode including a negative active material capable of intercalating/deintercalating lithium.
The negative active material may undergo volume expansion due to changes in the crystal structure that occur when lithium is intercalated and deintercalated. This volume expansion may cause cracks to form on the surface of the negative active material (and particularly, on the surface of the SEI layer on the negative electrode) during charge and discharge, leading to deterioration of the cycle-life characteristics of the battery.